In the manufacture of FPDs such as liquid crystal displays, semiconductor devices, CCDs, color filters or the like, photolithography has hitherto been used. For example, in a photolithographic process for producing integrated circuits, a positive- or negative-working resist is cast on a substrate, baked to remove the solvent, then exposed to radiation such as UV light, far UV light, electron beams or X-rays, and finally developed to form a resist pattern.
However, in many cases, the substrate used in the process has a high reflectance. Accordingly, in the exposure step, light passing through the resist layer is often reflected by the substrate and then reenters the resist layer, so that the light is applied to the resist layer even in areas not expected to be exposed. As a result, the aimed pattern often cannot be obtained or the obtained pattern may have unfavorable defects. Further, reflection of the light at the interface between the substrate and the resist layer often causes a standing-wave effect to corrugate the resist layer, and consequently serious troubles may occur in controlling the line width of the resist pattern. Those phenomena are remarkable particularly when light of a shorter wavelength is used in the exposure step for forming a finer pattern.
As a method for solving the above problems, it is proposed to provide a top anti-reflection coating. Specifically, for the purposes of reducing unfavorable reflection of light in the resist layer and thereby of improving the dimension accuracy, it is proposed that a top anti-reflection coating having a proper refractive index be formed on the top surface of the resist layer.
In order to attain the above purposes, it is studied to adopt a fluorine-containing compound as a component of the top anti-reflection coating (Patent documents 1 to 3). However, there are some points to improve. For example, in view of the safety, the fluorine-containing compounds disclosed in those documents have restrictions on the production process and on the use thereof. Further, since they have low solubility to water, it is necessary to use costly fluorine-containing solvents together. Although it is also studied to prepare a top anti-reflection coating composition by use of a fluorine-containing compound having improved solubility (Patent documents 4 and 5), the inventors have found that not all the compositions disclosed in the documents can have sufficient effects and hence that there are room for improvement to make the compositions satisfactory in all the respects, such as, film-formability, refractive index and temporal stability. In addition, although the low molecular weight fluorine compounds disclosed in Patent document 1 function as an essential component for realizing a low refractive index in the top anti-reflection coating, it is becoming difficult to employ them practically in consideration of the recent safety standards. Accordingly, it is desired to provide a top anti-reflection coating composition also satisfactory in safety.